(57) An automatic dialing apparatus (10) comprises a numeral entry device (47) for inputting numerals and a memory (22) for storing telephone directory numbers of authorized subscribers and their abbreviated dialing numbers in locations addressable as a function of the input numerals. For originating a call, the input numerals are used as an address pointer of the memory. An addressed telephone number is sent to a telephone switching system to allow a switched connection to be established to a called party and an addressed abbreviated dialing number is subsequently sent through the connection to the called party. On termination of the call to the called party, a coincidence is detected between the received abbreviated dialing number and an abbreviated dialing number assigned to the called party to verify authorization on detection of the coincidence. The latter is sent to the calling party to permit it to detect a coincidence between it and a copy of the number sent to the called party to verify authorization on detection of the last-mentioned coincidence.